The invention relates to a filter device for at least one electrical line that is connectable externally to a housing, for suppressing electromagnetic interference. In order to comply with electromagnetic compatibility in a device or installation with active electronics, the connecting lines generally have to be shielded from the outside or filtered. This also applies to signal lines in the low-voltage range.
For filtering connecting lines, it has become known heretofore to use filter plugs which are connectable to a printed circuit board or other components within a device.
At the present time, such filter plugs are available in a limited choice and are expensive. Furthermore, freedom in the design of the lines and the connection techniques and also the permissible current and voltage loads is greatly restricted.
It is accordingly an object of the invention to provide cost-effective filtering of the connecting lines which eliminates the disadvantages referred to hereinabove.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a filter device for at least one electrical line connectable externally to a housing, comprising at least one contact pin for connecting the externally connectable electrical line to a multilayer printed circuit board having at least one support layer and at least one conductor layer, the at least one contact pin having a part thereof located at a side of the filter device and being affixed to the printed circuit board, at least one outer layer of the printed circuit board being formed as one of a holohedral and a grid-shaped shielding layer, respectively, the shielding layer being in an electrically conductive contact-connection with the housing, at least one contact pin of a conductor path of the conductor layer conductable to the outside being connected to the printed circuit board, the at least one contact pin being arranged without electrical connection to the shielding layer, an electrical filter element connected to the at least one contact pin, the filter element having an electrical property corresponding to a selected value of the corresponding filtering, the filter element being electrically conductively connected to the shielding layer.
In accordance with another feature of the invention, the electrical filter element is a capacitor having a suitable capacitance.
In accordance with a further feature of the invention, the capacitor is connected to the shielding layer via a very low-inductive link.
In accordance with an added feature of the invention, the capacitor is connected directly to the at least one contact pin and the shielding layer.
In accordance with an additional feature of the invention, the direct connection is by Surface Mounting Device or SMD technology.
In accordance with yet another feature of the invention, the shielding layer is formed with a margin that is conductive all around to a suitable width.
In accordance with yet a further feature of the invention, the filter device includes connectors for effecting the connection between the printed circuit board and the housing, the spacing between the connecting points being selected in accordance with, respectively, electromagnetic compatability or EMC criteria and a low-impedance electromagnetic compatability or EMC seal arranged between the printed circuit board and the housing.
In accordance with yet an added feature of the invention, the filter device includes an inductor additionally connected in the conductor path upline of the capacitor.
In accordance with yet an additional feature of the invention, the connection of the inductor is effected by SMD technology.
In accordance with another feature of the invention, the filter device includes at least two different capacitor values used for a plurality of lines.
In accordance with a concomitant feature of the invention, different combinations of current and voltage lines are present.
Thus, the filter device for at least one electrical line that is to be connected externally to a housing comprises at least one contact for the connection of the line that is to be connected from outside the housing, and a multilayer printed circuit board having at least one support layer and at least one conductive layer. The filter-side part of the contact is affixed to the printed circuit board. In this regard, at least one outer layer of the printed circuit board is embodied as either a holohedral or grid-shaped shielding layer. Furthermore, the shielding layer is in electrically conductive contact-connection with the housing. At least one contact pin of a conductor track or path of the conductor layer that is to be routed to the outside is connected to the printed circuit board, the contact pin being arranged without electrical connection to the shielding layer. An electrical filter element is secured to the contact pin, the electrical properties of the filter element corresponding to the selected value of the corresponding filtering. In this regard, the filter element is electrically conductively connected to the shielding layer.
This type of embodiment has the advantage that, within a plug, individual filter values are possible for each individual line. Furthermore, for the filtering, there is no restriction to a standard plug type, so that it is possible to use not only plugs but also clamps. Moreover, a plurality of contact pins can be made accessible simultaneously on a board, only some of the pins, however, in any case being assigned to a plug, so that rearranging the plug results in different filtering.
A capacitor having a suitable capacitance is advantageously used as the electrical filter element.
The filter effect is further improved by connecting the capacitor to the shielding layer via a very low-inductive link, in which case the capacitor can be connected directly to the contact pin and the shielding layer, preferably using SMD technology. This direct connection, in particular, produces effective filtering of interfering influences.
The marginal edge of the shielding layer is preferably formed so that it is conductive all around to a suitable width, thereby ensuring an areal electrical connection between the printed circuit board and the housing.
This connection between the printed circuit board and the housing is produced by using a threaded or screw connection and/or a rivet connection. In this regard, the spacing between the connecting points is selected in accordance with EMC criteria and/or a low-impedance EMC seal is arranged between the printed circuit board and the housing.
In order to improve the filter effect further, an inductor may additionally be connected in the conductor track or path upline of the capacitor, preferably by the use of SMD technology.
If at least two different capacitor values are used in conjunction with a plurality of lines, then individual filtering of individual lines can be achieved within a plug.
In this regard, different combinations of current and voltage lines may be present in a plug or on a printed circuit board.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a filter device for at least one electrical line connectable externally to a housing, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: